The present invention relates to an air-bag device and a method for, folding the air-bag and particularly to a rapid opening performance of the air-bag realized by improving an airbag folding method and a diffusing plate for guiding a blown gas.
A generally known air-bag device installed in an automotive vehicle is comprised of an inflator (gas generator), an air-bag which is inflated upon the admittance of a gas generated by the inflator thereinto at the time of a crash, a container casing including a cover member made of a synthetic resin for covering the front sides of the inflator and the air-bag. When a crash sensor detects a crash, the inflator is activated to blow the gas to the air-bag to inflate it, thereby tearing the cover member open to expand to a passenger""s compartment to protect a passenger.
Generally, an air-bag device for a driver""s seat is installed in the middle of a steering wheel. An air-bag having a circular plan view in its inflated state is used for this air-bag device. An inflator and the folded air-bag of this air-bag device are accommodated in a container casing in the middle of a steering wheel while being folded. It should be noted that a steering pad of the steering wheel also serves as a cover member for covering the front sides of the air-bag and the inflator.
On the other hand, an air-bag having a substantially vertically long rectangular front view is used for an air-bag device for a passenger""s seat. An inflator and the folded air-bag of this air-bag device are accommodated in a container casing provided in the front or upper surface of a dashboard.
A variety of air-bag devices in which a folding method of an air-bag when the air-bag is to be accommodated in a container casing is devised have been put into practical use.
In the description under the caption xe2x80x9cprior artxe2x80x9d of the Japanese Unexamined Patent Publication No. 7-277125, a generally known folding method of the air-bag is mentioned. According to this folding method, after being transversely folded in a zigzag manner one fold over another from its opposite ends toward its middle, the air-bag is vertically folded in a zigzag manner one fold over another from its opposite ends.
In the air-bag device disclosed in the above publication, the air-bag is, after being folded first from its opposite ends toward its middle along a first direction and then rolled in an opposite direction (hereinafter, this folding method is referred to as an reverse roll-in method), folded in the reverse roll-in method along a second direction perpendicular to the first direction, and then accommodated in a container casing.
Further, in an air-bag device disclosed in Japanese Unexamined Patent Publication No. 9-263204, an air-bag is, after being folded in a zigzag manner one fold over another from its opposite ends toward its middle along a direction corresponding to a vertical direction in an inflated state of the air-bag, transversely folded in the reverse roll-in method from its left and right ends toward its middle, and is then accommodated in a container casing. This publication also discloses a construction of the air-bag device in which an air-bag is, after being folded in a zigzag manner one fold over another from its opposite ends toward its middle along a direction substantially corresponding to a vertical direction in an inflated state of the air-bag, transversely folded in a zigzag manner one fold over another.
Generally speaking, there are three folding methods of the air-bag: a zigzag folding method according to which the air-bag is vertically or transversely folded in a zigzag manner one fold over another from its opposite sides toward its middle; a roll-in method according to which the air-bag is vertically or transversely rolled in from its opposite sides toward its middle; and a reverse roll-in method according to which the air-bag is vertically or transversely folded first from its opposite ends toward the middle and then rolled in an opposite direction.
The air-bag folded in the zigzag folding method is easy to rapidly inflate, whereas the air-bag folded in the roll-in method or the reverse roll-in method is inflated at a slightly reduced speed. Further, the air-bag folded in the zigzag folding method causes a large impact on the passenger since the air-bag is likely to expand toward the passenger. The air-bag folded in the roll-in method also causes a large impact on the passenger for the same reason.
According to the prior art air-bag folding method disclosed in Japanese Unexamined Patent Publication No. 7-277125 (transversely and vertically folded in a zigzag manner), the air-bag is difficult to rapidly expand to the left and right sides since it is likely to rapidly expand toward the passenger while being inflated. According to another air-bag folding method disclosed in this publication (reverse roll-in method in both first and second directions), it is difficult to speed up the inflation of the air-bag since the air-bag is folded in the reverse roll-in method in both directions.
According to the air-bag folding method disclosed in Japanese Unexamined Patent Publication No. 9-263204 (vertically folded in a zigzag manner and transversely folded in the reverse roll-in method), it is difficult to speed up the inflation of the air-bag at an early stage thereof since the zigzag folds are vertically expanded after the folds made in the reverse roll-in method are transversely expanded. According to another air-bag folding method disclosed in this publication (vertically and transversely folded in a zigzag manner), although the inflation to the left and right sides can be slightly speeded up, it is difficult to sufficiently speed up the transverse inflation of the air-bag since the air-bag is likely to expand toward the passenger.
It is an object of the present invention to suppress an inflation (expansion) of an air-bag of an air-bag device toward a passenger at an early stage of the inflation, to promote a transverse inflation of the air-bag more than a vertical inflation thereof at an early stage of the inflation, and to restrict a blow out of a gas toward the passenger.
In order to fulfill the above object according to this invention, an air-bag device, comprises an inflator; an air-bag to be inflated by a gas supplied from the inflator; and a cover member adapted for covering front sides of the inflator and the air-bag and to be split open upon inflation of the air-bag, said air-bag is accommodated under the cover member in such a folded state that: opposite ends of the air-bag along a first axis are folded towards its middle along the first axis and are rolled in a direction opposite to the folding direction along the first axis, and opposite ends of the air-bag along a second axis, perpendicular to the first axis, are folded in a zigzag manner one fold over another along the second axis.
These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings.